1. Technical Field
The present invention relates in general to a disk drive device and, in particular, to an improved method and system for performing positioning control of a head actuator in a disk device. Still more particularly, the present invention relates to a method and system for o optimizing the performance of head actuator control of disk devices of different sizes, having different characteristics, utilizing a multi-purpose programmable digital filter to perform servo control.
2. Description of the Prior Art
Greater miniaturization and reliability are being demanded in hard disk drives (HDDs) utilized as external storage devices in information-processing equipment.
As depicted in FIG. 2, concentric recording tracks X2 are formed on the recording surface of a magnetic disk utilized as a recording medium in a fixed disk device. Servo areas X3, in which a servo pattern, ID, and the like are recorded at constant angles, are provided at certain angles in recording tracks X2. Data areas X4, in which data sectors X5 are recorded at a constant angular velocity, are provided between adjacent servo areas X3. In some fixed disk devices of this type, these data areas X4 are divided into several areas (zones) in the radial direction, and the number of data sectors X5 recorded in each zone is made responsive to the radial position to produce a more uniform recording density.
In these fixed disk devices, when a sector is specified and recording or reproduction is commanded, seek control is performed to move a head X6 to the track in which the sector to be recorded or reproduced is recorded (the target track). After head X6 has reached the target track, following control is carried out to adjust the position of head X6 so that head X6 follows the track.
A disk drive device possesses a hard disk controller (HDC) X9 that moves a head arm X7 according to an error between the present position of head X6 and the target track, thereby carrying out servo control, such as seek control and following control.
As depicted in FIG. 3, a disk servo pattern (WEDGE-A, WEDGE-B, WEDGE-C, WEDGE-D) and an ID (CYLID) are recorded in servo area X3; when head X6 passes over these, the reproduced outputs of the servo pattern and ID, reproduced by head X6, are supplied to HDC X9. When supplied with these reproduced outputs, HDC X9 determines from them the present position of head X6, and finds the error (track displacement) with respect to the target track. Upon determining the track displacement, HDC X9 determines data (DACOUT value) therefrom for driving a voice coil motor (VCM) X8 that moves head arm X7.
In seek control, HDC X9 determines the difference between the present position of head X6 and the position of the target sector (the track displacement), and carries out control in response to this track displacement.
When a target track is designated, first, control is executed to accelerate head X6 toward the target sector. Next, when the velocity of motion of head X6 reaches a certain velocity, HDC X9 executes control to move head X6 at a constant velocity. Finally, when head X6 reaches the vicinity of the target sector, control (settling control) is executed to decelerate head X6.
When head X6 reaches the target track, there is a switchover to following control to make head X6 follow the target track. These control switchovers are carried out by changing parameters of the calculations that determine the DACOUT values.
Components of resonant frequencies of the actuator system, including head arm X7, are included in the DACOUT values determined as described above, however, and there have been cases in which, when VCM X8 was driven directly according to these types of DACOUT values during seeking, positioning control of the head became unstable. Efforts have been made to stabilize servo control by reducing the resonant frequency components of the DACOUT values by inserting a notch filter with a notch characteristic to suppress mechanical resonances, as depicted in U.S. Pat. No. 5,325,247, for example. A plurality of mechanical resonances can be dealt with in this way by coupling a plurality of notch filters in series.
If the pass characteristic is flat on the low side, then control may fail to stabilize during track following, because of disk eccentricity, disturbances, and the like. Efforts have therefore been made to stabilize control by calculating a narrow-band peak filter in parallel with servo control and adding the peak filter to the output to deal with low-frequency disturbances arising from disk-shift, unbalance, and the like, as described in U.S. Pat. No. 5,608,586, for example.
To realize this type of control, multiple filters with different characteristics were provided in fixed disk devices, and the filters to be utilized were selected according to the operating mode, or the operation of each filter was controlled.
There have been problems, however, in this conventional type of disk device. In particular, to control the head actuators of disk devices of different sizes, having different characteristics, it is necessary to design logic including filter characteristics for the particular hardware, because the characteristics of the filters needed in each type of disk device, such as peak filters for disturbance suppression and notch filters for mechanical resonance suppression, differ. For example, with the small actuators employed in hard disks with a form factor of one inch or less, the resonant frequencies become extremely high, and it becomes less necessary to insert the above-mentioned notch filters in series, but the disk becomes extremely thin, and the problem of repeatable disturbances due to disk eccentricity, warping, and the like arises.
Also, to realize control, it was necessary to provide complex data tables, by a microprocessor, or by a tester that tested the drive, to identify the mechanical resonant frequencies and adjust the filter coefficients. In real time, self-tuning the filter coefficients was difficult.
It should therefore be apparent that it would be preferable to provide a digital filter, a servo control device, and a disk drive device in which the filter configuration can be altered according to purpose, and disturbance suppression and mechanical resonance suppression can be effectively carried out.
Further, it is preferable to provide a digital filter, a servo control device, and a disk drive device that can easily generate variable-frequency noise for measuring frequency characteristics, and can measure actuator frequency characteristics in real time.
In view of the foregoing, it is therefore an object of the present invention to provide an improved disk drive device.
It is another object of the present invention to provide an improved method and system for performing positioning control of a head actuator in a disk device
It is yet another object of the present invention to provide and improved method and system for optimizing the performance of head actuator control of disk devices of different sizes, having different characteristics, utilizing a multi-purpose programmable digital filter to perform servo control.
In accordance with the method and system of the present invention multiple selectable filter modules are provided. Each of the multiple selectable filter modules functions in a serial or parallel filtering mode when selected. Multiple configurable registers are also provided wherein the configuration of each of the multiple configurable registers determines a selection of at least one of the multiple selectable filter modules. Particular ones of the multiple configurable registers are selected, such that a configuration of the digital filter is dynamically selectable in order to achieve a predetermined filter output.
All objects, features and advantages of the present invention will become apparent in the following detailed written description.